bro = []
for i in range(3):
  bro.append(int(input()))
a = bro[0]
b = bro[1]
c = bro[2]
bro.sort(reverse=True)

for i in bro:
  if i == a:
    print('A')
  elif i == b:
    print('B')
  elif i == c:
    print("C")